Tailoring wood-based activated carbons and assessing the role of impregnation and O₂ for efficient H₂S removal from biogas

This study presents the synthesis and evaluation of steam-activated carbons (ACs) derived from hard wood for biogas desulfurization. Optimum H₂S removal was achieved with ACs featuring well-balanced ultramicroporosity and microporosity, which proved more effective than mesoporosity. Three ACs were impregnated with KOH, KI and K₂CO₃ at loadings from 5 to 30 wt%. A 10 wt% impregnation rate was identified as optimal for all agents, with KOH showing superior performance, particularly under oxidizing conditions. Dynamic adsorption experiments were performed using humidified ACs and gas mixtures containing either 400 ppm or 4000 ppm H₂S in 60% N₂ and ∼40% CO₂, without O₂ or with 1.1% O₂. Indeed, H 2 O and O₂ presence significantly improved H₂S removal by up to three and eight times, respectively. O₂ also extended breakthrough times by up to a factor of ten. When benchmarked against nine commercial ACs, the optimum wood-derived AC demonstrated superior mass-based adsorption capacity but lower volumetric performance due to its low bulk density, indicating the need for densification strategies. A one-dimensional model was also developed, validated against experimental data, and applied under realistic gas compositions including humidified ACs, CO₂ and O₂, conditions rarely addressed in prior studies. The model accurately predicted breakthrough behaviour and provided mass transfer coefficients, establishing it as a reliable tool for process design, optimization, and future material development. • Wood-based activated carbons were tested for H₂S removal, both as such and impregnated. • 10 wt% KOH impregnation optimized AC performance, matching commercial standards. • Humidified ACs tripled H₂S capacity vs. dry, showing key role of H₂O in the process. • Adding 1.1% O₂ increased H₂S removal 8 × and extended breakthrough time 10 ×. • A validated 1D model predicts breakthrough behaviour and gives mass transfer coefficients.